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How to time Trial in the wind(8 posts)

How to time Trial in the windflipflop
Aug 6, 2003 3:26 AM
I've got an out and back TT coming up. Last time there was a strong head wind on the way out. Should I try to conserve a little bit for a stronger ride back or go hard out into the wind? (When there is little to no wind) I do the best if I hold my heart rate @ 182. Last time I didn't have much left when I turned around even though I was holding my heart rate @ 182.
re: How to time Trial in the windTime Trial dot org
Aug 6, 2003 6:53 AM
"Wind is the time trialist's nemesis. A windy day is always a slow day. And no matter how much faster you go with a tail wind, you'll lose that extra time and more when you turn around and face it. Head winds are the worst, but crosswinds can be almost as bad.

Wind, however, is a fact of life in time trials. And every cyclist is out there under the same conditions. So you need to fight the wind effectively to do well. Start with a good aerodynamic position. Always important, your position on the bicycle becomes vital in windy conditions when the effect of any body part protruding more than necessary into the slipstream is magnified. Keep low on the bicycle. "

http://www.timetrial.org/whatistimetrial.htm
re: How to time Trial in the windtigermilk
Aug 6, 2003 9:12 AM
Going into the wind is like going uphill. More effort there and getting your energy back on the downhill or with the wind is the best strategy. For example, doing a 40k at 300 W, CdA=.3 m^2, rolling friction of .004, and sea-level conditions on an 85 F day yields a 25.68 mph average. If you throw a 10 mph head/tail wind in there and ride at constant power that's down to 24.54 mph. If you ride into the wind at 315 W (5% more effort) and back at 282 W (6% less), you perform the same amount of work but the overall speed bumps up to 24.72 mph (a savings of 27 seconds for the 40k). The key is to not go too hard going out into the wind and not having anything left in the end.
Not disputing your math or your conclusion...TFerguson
Aug 6, 2003 4:55 PM
only your first line analogy. "Going into the wind is like going uphill."

Going uphill gives a better time because there is less drag per power required. This is especially beneficial vs a pack because they can share the wind drag but not the hill.

In the out-and-back with wind, the downwind section is more like the uphill because, here, the forces other than wind drag also play a larger role. This is why slightly more effort pays off downwind. The effort is going against non-wind drag forces rather than the exponetially increasing (with speed) wind drag.

I'm just thinking out loud here trying to make sense of it myself. Am I making sense or just rambling?

TF
Not disputing your math or your conclusion...tigermilk
Aug 7, 2003 9:12 AM
Downwind=riding with the wind --> like going downhill
Upwind=riding into the wind --> like going uphill

Looking at just the aero and grade portions of the power equation:

P=rho*CdA*Vt^2*Vg/2+m*g*grade*Vg

where rho is air density, Vt is true velocity, Vg is ground speed, m is mass, g is gravity constant. If going into a headwind, Vt=Vg+Vw (Vw=wind speed). With the wind, Vt=Vg-Vw.

Play with that and you'll find that going uphill is like going into the wind, and that going gangbusters with the wind or down a hill won't give you the time savings you'd get pushing into the wind or uphill.

Also check out http://briefcase.yahoo.com/bc/tigermilk@sbcglobal.net

Go to Cycling, Show All, and download power_tt.xls It's a simple spreadsheet I wrote to demonstrate time trial strategies.
mash or spin?yeah right
Aug 6, 2003 1:03 PM
That's always my issue. I normally like to keep my cadence up rather than push big gears, but I find myself mashing when I'm riding into a headwind. In tt's I pretty much try and keep the exertion the same, but how I get the power out is the question.
mash or spin?RIAN
Aug 7, 2003 12:27 AM
If its a headwind start, its vital that you warm up properly. Holding form and position are also vital and you need to concentrate more than usual. Once you have found the speed you can hold at one or two beats above your normal hr for the distance, you have to concentrate on keeping as close to that speed as you can. You will spend more time on the headwind leg, so even a small loss of speed will have an exaggerated effect on your time. I always find that the morale/adrenelin boost on the downwind leg outweighs the fatigue of fighting a headwind on the way out. Cadence should be no different from windless conditions. If you normally aim for 90 that should still be your target, but in a lower gear.
mash or spin?Jon Billheimer
Aug 7, 2003 7:53 AM
Good point about maintaining cadence. I think it's natural as soon as we encounter resistance--whether from the wind or on hills--to hold a gear and reduce cadence. The whole issue is largely psychological. One tactic which I find helps to maintain concentration and to stay relaxed is to ride tt's with ear plugs. The sound of the wind in one's ears tends to make one tense up and start thrashing around. With earplugs on you can concentrate on your cadence and the sound of your own breathing. This helps quite a bit. The more internally focused you can remain the better.